<!doctype html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>无标题文档</title>
        <style type="text/css">
            *{ padding:0; margin:0; list-style:none; border:0;}
            .all{
                width:500px;
                height:200px;
                padding:7px;
                border:1px solid #ccc;
                margin:100px auto;
                position:relative;
            }
            .screen{
                width:500px;
                height:200px;
                overflow:hidden;
                position:relative;
            }
            .screen li{ width:500px; height:200px; overflow:hidden; float:left;}
            .screen ul{ position:absolute; left:0; top:0px; width:3000px;}
            .all ol{ position:absolute; right:10px; bottom:10px; line-height:20px; text-align:center;}
            .all ol li{ float:left; width:20px; height:20px; background:#fff; border:1px solid #ccc; margin-left:10px; cursor:pointer;}
            .all ol li.current{ background:yellow;}
    
            #arr {display: none;}
            #arr span{ width:40px; height:40px; position:absolute; left:5px; top:50%; margin-top:-20px; background:#000; cursor:pointer; line-height:40px; text-align:center; font-weight:bold; font-family:'黑体'; font-size:30px; color:#fff; opacity:0.3; border:1px solid #fff;}
            #arr #right{right:5px; left:auto;}
        </style>

    <script>
        window.onload = function (){
			
			//需求:无缝滚动
			//思路:复制第一张图片放到ul的最后,然后当图片切换到第五张的时候直接切换第六张,再次从第一张切换到第二张的时候先瞬间切换到第一张图片,然后滑动到第二张图片.
			//步骤:
			//1.获取事件源及相关元素.
			//2.复制第一张图片所在li,添加到ul后面
			//3.给ol中添加li,ul中的个数-1个,并点亮第一个按钮.
			//4.鼠标放到ol的li上切换图片
			//5.添加定时器
			//6.左右切换图片(鼠标放上去隐藏，移开显示)
			
			//步骤:
			//1.获取事件源及相关元素.
			var all = document.getElementById("all");
			var screen = all.firstElementChild || all.firstChild;
			var imgWidth = screen.offsetWidth;
			var ul = screen.firstElementChild || screen.firstChild;
			var ol = screen.children[1];
			var div = screen.lastElementChild || screen.lastChild;
			var spanArr = div.children;
			
			//2.复制第一张图片所在li,添加到ul后面
			var ulNewLi = ul.children[0].cloneNode(true);
			ul.appendChild(ulNewLi);
			//3.给ol中添加li,ul中的个数-1个,并点亮第一个按钮.
			for(var i=0;i<ul.children.length-1;i++){
				var olNewLi = document.createElement("li");
				olNewLi.innerHTML = i+1;
				ol.appendChild(olNewLi)
			}
			var olLiArr = ol.children;
			olLiArr[0].className = "current";
			//4.鼠标放到ol的li上切换图片
			//5.添加定时器
			//6.左右切换图片(鼠标放上去隐藏，移开显示)
			
		}
    </script>
</head>

<body>
<div class="all" id='all'>
    <div class="screen" id="screen">
        <ul id="ul">
            <li><img src="images/1.jpg" width="500" height="200" /></li>
            <li><img src="images/2.jpg" width="500" height="200" /></li>
            <li><img src="images/3.jpg" width="500" height="200" /></li>
            <li><img src="images/4.jpg" width="500" height="200" /></li>
            <li><img src="images/5.jpg" width="500" height="200" /></li>
        </ul>
        <ol>

        </ol>
        <div id="arr">
            <span id="left"><</span>
            <span id="right">></span>
        </div>
    </div>
</div>
</body>
</html>
